Cereal cover crop response to N fertilizer

Authors: Balkcom, Kipling

Submitted to: Extension Publications
Publication Type: Experiment Station
Publication Acceptance Date: 9/26/2019
Publication Date: 9/26/2019
Citation: Balkcom, K.S. 2019. Cereal cover crop response to N fertilizer. Alabama Cooperative Extension Systems. Available at https://www.aces.edu/blog/topics/row-cover-crop-soils/cereal-cover-crop-response-to-nitrogen-fertilizer/.

Interpretive Summary: A winter cover crop can benefit the soil and/or subsequent crop, but cover crops are not harvested for feed or sold as a commodity. Cover crop benefits include soil erosion protection, increased soil organic C accumulation, weed suppression, and soil moisture conservation. Coarse-textured soils and high average rainfall amounts combine to limit inorganic N available for uptake so N fertilizer applications can ensure adequate cereal biomass production. Information about expected biomass levels produced from N fertilizer helps growers manage biomass production costs within their cover crop goals. An ARS scientist in Auburn, AL conducted a study at the Wiregrass Research and Extension Center in Headland, Alabama that compared biomass production for oat, rye, and ryegrass (Lolium multiflorum L.) across four N rates (0, 30, 60, and 90 lb N/ac.). Average biomass production was 5510 lb/ac for ‘Wrens Abruzzi’ rye, 4230 lb/ac for ‘Harrison’ oat and 2510 lb/ac for ‘Marshall’ ryegrass. Rye and oat performed similarly across N rates, while ryegrass lagged behind for all measured values. Single species winter cereal cover crops like rye and oat benefit from N fertilizer applications by enhancing biomass levels and benefits.

Technical Abstract: A winter cover crop can benefit the soil and/or subsequent crop, but cover crops are not harvested for feed or sold as a commodity. Cover crop benefits include soil erosion protection, increased soil organic C accumulation, weed suppression, and soil moisture conservation. Coarse-textured soils and high average rainfall amounts combine to limit inorganic N available for uptake so N fertilizer applications can ensure adequate cereal biomass production. Information about expected biomass levels produced from N fertilizer helps growers manage biomass production costs within their cover crop goals. A four-year experiment (2009-2012) was conducted in Headland, AL. Biomass production for oat (Avena sativa L.), rye (Secale cereale L.), and ryegrass (Lolium multiflorum L.) was compared across four N rates (0, 30, 60, and 90 lb N/ac.) applied as ammonium nitrate. All cover crops were established between the 1st and 3rd week of Nov. and terminated between the 2nd and 3rd week of April. Average biomass production was 5510 lb/ac for ‘Wrens Abruzzi’ rye, 4230 lb/ac for ‘Harrison’ oat and 2510 lb/ac for ‘Marshall’ ryegrass. Average biomass production varied by growing season and differences were attributed to rainfall and growing degree days. Rye and oat performed similarly across N rates, while ryegrass lagged behind for all measured values. Single species winter cereal cover crops like rye and oat benefit from N fertilizer applications by enhancing biomass levels and benefits.